U.S. patent number 8,317,838 [Application Number 12/328,914] was granted by the patent office on 2012-11-27 for system and method for minimally invasive posterior fixation.
This patent grant is currently assigned to Warsaw Orthopedic. Invention is credited to Michael R. Henson, Thanh V. Nguyen, To V. Pham, Samuel M. Shaolian, George P. Teitelbaum.
United States Patent |
8,317,838 |
Nguyen , et al. |
November 27, 2012 |
System and method for minimally invasive posterior fixation
Abstract
The present invention relates generally to systems and methods
for aligning and implanting orthopedic fixation or stabilization
implants within the body. In one embodiment, the system includes at
least two bone anchors, at least one of which is provided with an
angularly adjustable connector. In one aspect, the system also
includes at least one linkage rod, for linking two or more bone
anchors through their respective adjustable connectors. The bone
anchors and the linkage rod may be locked into place to form a
spinal fusion or fixation prosthesis. An alignment tool is
provided, for guiding a guidewire through one or more
connectors.
Inventors: |
Nguyen; Thanh V. (Irvine,
CA), Shaolian; Samuel M. (Newport Beach, CA), Teitelbaum;
George P. (Santa Monica, CA), Henson; Michael R. (Coto
de Caza, CA), Pham; To V. (Trabuco Canyon, CA) |
Assignee: |
Warsaw Orthopedic (Warsaw,
IN)
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Family
ID: |
42561184 |
Appl.
No.: |
12/328,914 |
Filed: |
December 5, 2008 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20090082809 A1 |
Mar 26, 2009 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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10462098 |
Jun 13, 2003 |
7473267 |
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Current U.S.
Class: |
606/279 |
Current CPC
Class: |
A61B
17/7082 (20130101); A61B 17/1671 (20130101); A61B
17/7086 (20130101); A61B 17/704 (20130101); A61B
17/7083 (20130101); A61B 17/1757 (20130101); A61B
17/7001 (20130101); A61B 17/7019 (20130101); A61B
17/7089 (20130101); A61B 17/90 (20210801); A61B
17/1642 (20130101); A61B 17/861 (20130101); A61B
17/3468 (20130101); A61B 17/7011 (20130101); A61B
17/3472 (20130101); A61B 17/702 (20130101); A61B
17/864 (20130101); A61B 17/7005 (20130101); A61B
17/8897 (20130101); A61B 17/7004 (20130101); A61B
17/8861 (20130101); A61B 17/1615 (20130101) |
Current International
Class: |
A61B
17/88 (20060101) |
Field of
Search: |
;606/53,60,96,98,99,103,104,246,264-270,279 |
References Cited
[Referenced By]
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Foreign Patent Documents
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WO9730666 |
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WO |
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Apr 2001 |
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WO |
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Jan 2002 |
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WO |
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WO02076315 |
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Oct 2002 |
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WO |
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Other References
Supplementary European Search Report for European Patent
Application No. 04760245 (the European Counterpart of the present
Application, mailed Sep. 18, 2008). cited by other .
International Search Report for European Application No. 00 98 9371
(The European counterpart of the parent application) mailed Jan. 2,
2007. cited by other .
International Search Report for European Application No.
PCT/US04/10902 (The PCT counterpart of the parent application).
cited by other .
Muller et al. "A Keyhole Approach for Endoscopically Assisted
Pedicle Screw Fixation in Lumbar Spine Instability". Neurosurgery,
vol. 47, No. 1, Jul. 2000, pp. 85-96. cited by other .
European Patent Office European Search Report, EP Patent
Application No. 04 760 245.3-2310, Oct. 25, 2010. cited by other
.
European International Search Report mailed on Aug. 12, 2009. cited
by other.
|
Primary Examiner: Truong; Kevin T
Assistant Examiner: Araj; Michael
Parent Case Text
This application is a divisional of co-pending U.S. application
Ser. No. 10/462,098, filed Jun. 13, 2003, the entire contents of
which are hereby incorporated by reference.
RELATED APPLICATIONS
This application claims priority under 35 U.S.C. .sctn.119(e) to
U.S. Provisional Application No. 60/465,902 filed on Apr. 25, 2003,
the disclosure of which is incorporated by reference in its
entirety herein.
Claims
What is claimed is:
1. A method for minimally invasive posterior fixation, comprising:
securing a bone anchor to a vertebral body, said bone anchor
provided with an adjustable connector; advancing a trocar having a
removable cap connected to a second portion of the trocar having a
sharp tipped cannula wherein removing the cap exposes a lumen
configured to receive a guide wire; inserting a guide wire into the
lumen and advancing the guide wire to a desired position; removing
the trocar; inserting a rod over a guide wire along an arcuate path
through said adjustable connector; and adjusting said adjustable
connector to fix said rod with respect to said bone anchor.
2. The method of claim 1 further comprising: securing a second bone
anchor to a second vertebral body, said second bone anchor provided
with a second adjustable connector; inserting said rod through said
second adjustable connector; and securing said second adjustable
connector to fix said rod with respect to said second bone
anchor.
3. The method of claim 2 wherein said first vertebral body and said
second vertebral body are adjacent vertebral bodies.
4. The method of claim 2 wherein said first vertebral body and said
second vertebral body are separated by one or more other vertebral
bodies.
5. The method of claim 1 wherein said guide wire is inserted via an
access needle provided at the end of a handle which is attached at
a pivot to a driver aligned with a central axis of said first bone
anchor, whereby said handle is pivoted about said pivot to insert
said access needle through said first rotating connector.
6. The method of claim 1, wherein the bone anchor includes a first
aperture, the method further comprises: securing a second bone
anchor, having a second aperture, to a second vertebral body;
providing a curved guide needle; advancing the guide needle through
at least one of the first and second apertures; and advancing the
guide wire through the first and second apertures.
7. The method of claim 6, wherein the first and second vertebral
bodies are adjacent vertebral bodies.
8. The method of claim 6, wherein the first and second vertebral
bodies are separated by a third vertebral body.
9. The method of claim 6 wherein the guide needle has a radius of
curvature within the range of from about 6 cm to about 15 cm.
10. The method of claim 6, additionally comprising the step of
advancing a fixation device along the guide wire.
11. The method of implanting spinal fusion hardware as in claim 10,
wherein the advancing a fixation device step comprises advancing an
inflatable fixation device.
12. The method of claim 10, wherein the advancing a fixation device
step comprises advancing a preformed, rigid fixation device.
13. The method of claim 6, additionally comprising the step of
advancing a guide tube along the guide wire and through the first
and second apertures.
14. The method of claim 13, additionally comprising the step of
advancing a fixation device through the guide tube.
15. The method of claim 1 further comprising: securing a second
bone anchor to a second vertebral body; advancing the guide wire
through a tissue tract to the bone anchor; deflecting the guide
wire in between the bone anchor and the second bone anchor; and
advancing the guide wire to the second bone anchor.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to medical devices and,
more particularly, to systems for aligning and implanting
orthopedic fixation or stabilization implants within the body. In
one application, the present invention relates to minimally
invasive procedures and devices for implanting posterior
instrumentation.
2. Description of the Related Art
The human vertebrae and associated connective elements are subject
to a variety of diseases and conditions which cause pain and
disability. Among these diseases and conditions are spondylosis,
spondylolisthesis, vertebral instability, spinal stenosis and
degenerated, herniated, or degenerated and herniated intervertebral
discs. Additionally, the vertebrae and associated connective
elements are subject to injuries, including fractures and torn
ligaments and surgical manipulations, including laminectomies.
The pain and disability related to these diseases, conditions,
injuries and manipulations often result from the displacement of
all or part of a vertebra from the remainder of the vertebral
column. A variety of methods have been developed to restore the
displaced vertebrae or portions of displaced vertebrae to their
normal position and to fix them within the vertebral column. For
example, open reduction with screw fixation is one currently used
method. The surgical procedure of attaching two or more parts of a
bone with pins, screws, rods and plates requires an incision into
the tissue surrounding the bone and the drilling of one or more
holes through the bone parts to be joined. Due to the significant
variation in bone size, configuration, and load requirements, a
wide variety of bone fixation devices have been developed in the
prior art. In general, the current standard of care relies upon a
variety of metal wires, screws, rods, plates and clamps to
stabilize the bone fragments during the healing or fusing process.
These methods, however, are associated with a variety of
disadvantages, such as morbidity, high costs, lengthy in-patient
hospital stays and the pain associated with open procedures.
Therefore, devices and methods are needed for repositioning and
fixing displaced vertebrae or portions of displaced vertebrae which
cause less pain and potential complications. Preferably, the
devices are implantable through a minimally invasive procedure.
SUMMARY OF THE INVENTION
In accordance with one aspect of the present invention, a system is
provided for the minimally invasive implantation of posterior
fixation hardware. The system generally includes at least two bone
anchors, at least one of which is provided with an adjustable
connector. In many clinical situations, all of the bone anchors
used in the system may be provided with adjustable connectors. The
system may also include a driver for inserting the bone anchor into
a bone and locking the adjustable connector. The system also
includes at least one linkage rod, for linking two or more bone
anchors through their respective adjustable connectors. In one
embodiment, an insertion tool is provided for the insertion of the
linkage rod. The bone anchors and the linkage rod may be fixed to
each other by the locking of the adjustable connectors on the bone
anchors, to subcutaneously form a prosthesis.
In accordance with another aspect of the present invention, the
system additionally includes a guidance apparatus for the minimally
invasive implantation of posterior fixation hardware. In one
embodiment, the guidance apparatus includes a central support arm
adapted to engage a bone anchor. A radial arm is pivotably attached
to the central arm. A hollow access needle is secured to the radial
arm. The radial arm is pivotable with respect to the central arm,
to allow the hollow access needle to travel along an arcuate path,
for guiding a guidewire through a tissue tract and into and through
at least one adjustable connector on a bone anchor (or bone screw).
The hollow access needle may removably carry an obturator, to
facilitate percutaneous advancement. The hollow needle may
additionally removably carry a distal guidewire capture device, for
capturing a proximally advancing guidewire subcutaneously within
the hollow access needle. The guidewire capture device may comprise
a radially enlargeable structure such as a conical funnel, for
deflecting an approaching guidewire into the lumen of the hollow
access needle.
In another aspect of the present invention, a method is provided
for the minimally invasive implantation of posterior fixation
hardware. In one embodiment, the method comprises the insertion of
a first bone anchor, having a first adjustable connector, into a
first vertebral body. A second bone anchor, having a second
adjustable connector, is inserted into a second vertebral body. The
first and second vertebral bodies may be adjacent to each other, or
separated by one or more other vertebral body or bodies. A linkage
rod is inserted through the adjustable connectors of both bone
anchors. The adjustable connector of each bone anchor is then
locked, fixing the position of the adjustable connector within the
bone anchor, and securing the linkage rod within the adjustable
connector, to form a prosthesis.
In accordance with another embodiment of the present invention, the
method further comprises the insertion of another bone anchor with
an adjustable connector into another vertebral body. This latter
vertebral body may be adjacent to either or both of the first and
second vertebral bodies, or separated from both the first and
second vertebral bodies. The linkage rod is inserted through the
adjustable connectors of all of the bone anchors to form the
prosthesis.
In accordance with another embodiment of the present invention, the
method additionally includes the placement of one or more guide
wires. A guide wire may be inserted into a bone to define a path
for the insertion of a bone anchor. Another guide wire may be
threaded through the adjustable connectors of two or more bone
anchors, to guide the insertion of the linkage rod. The guide wire
may be placed using the guidance apparatus described above.
In any of the foregoing systems and methods, the guide wire may be
replaced or supplemented by a flexible guide tube. In such
implementations of the invention, the bone anchor and/or the
linkage rod may be advanced through the interior of the guide
tube.
Further features and advantages of the present invention will
become apparent to those skilled in the art in view of the detailed
description of preferred embodiments which follows, when considered
together with the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an overview of a system for minimally invasive posterior
spinal fixation according to one embodiment of the present
invention.
FIG. 2 is an exploded view of the bone anchor and the driver of
FIG. 1.
FIG. 3A is an enlarged view of the circled area in FIG. 2.
FIG. 3B illustrates an angularly adjustable connector with rotation
limits according to another embodiment.
FIG. 3C illustrates a connector, a locking cap and its
complementary inner adapter according to yet another
embodiment.
FIGS. 3D-3F illustrate the connector illustrated in FIG. 3C in
further detail.
FIG. 3G is a cross-sectional view of an angularly adjustable
connector with rotation limits positioned within a head of a bone
anchor according to another embodiment.
FIG. 4 is another view of the system for minimally invasive
posterior spinal fixation illustrated in FIG. 1, with the linkage
rod detached from its insertion tool.
FIG. 5 is an enlarged view of the circled area in FIG. 4.
FIG. 6 is another view of the system for minimally invasive
posterior spinal fixation illustrated in FIG. 4.
FIGS. 7-12 illustrate the use of positioning tools to position a
guide wire into a vertebral body.
FIGS. 13-14 illustrate the use of a dilation balloon catheter to
dilate a tissue tract.
FIGS. 15-20 illustrate the positioning of a sheath adjacent to a
vertebral body.
FIGS. 21-23 illustrate a drill used to create an opening in a
vertebral body to receive a bone anchor.
FIGS. 24-25 illustrate advancing a bone anchor over the wire
towards a vertebral body.
FIGS. 26-27 illustrate a bone anchor and the driver used to insert
the bone anchor into a vertebral body.
FIGS. 28-31 illustrate the use of the driver to insert a bone
anchor into a vertebral body.
FIG. 32 illustrates two bone anchors positioned in two adjacent
vertebral bodies.
FIG. 33 illustrates an alignment device for positioning a guidewire
though a bone anchor in accordance with one aspect of the present
invention.
FIG. 34 illustrates a flexible obturator for positioning within the
arcuate arm of the alignment device.
FIG. 35 illustrates a first alignment device coupled to first bone
anchor, and a second alignment device coupled to a second bone
anchor.
FIGS. 36 and 37 illustrate a guidewire capture device, for
positioning within the arcuate arm on an alignment device.
FIG. 38 illustrates the first and second alignment devices, with a
guidewire advancing from the first alignment device towards the
capture device carried by the second alignment device.
FIG. 39 is an illustration as in FIG. 38, after the guidewire has
entered the guidewire capture device and traversed the curved arm
on the second alignment device.
FIG. 40 is a side elevational view of a linkage rod, decoupled from
an insertion tool, both over a guidewire.
FIG. 41 is a side elevational perspective view of a guidewire
positioned through two adjacent bone anchors, and a linkage rod
being advanced along the guidewire by an insertion tool.
FIG. 42 is an illustration as in FIG. 41, with the linkage rod
positioned within the first and second bone anchors.
FIG. 43 is an illustration as in FIG. 42, with a driver in position
to lock the first bone anchor to the linkage rod.
FIG. 44 is an illustration as in FIG. 43, with a portion of the
driver tool proximally retracted.
FIG. 45 is an illustration as in FIG. 44, with the driver tool
retracted, the first and second bone anchors locked onto the
linkage rod, and the insertion tool decoupled from the linkage
rod.
FIG. 46 is an illustration as in FIG. 45, with the insertion tool
and the guidewire removed from the linkage rod, illustrating a
formed in place one level posterior fusion device in accordance
with the present invention.
FIG. 47 is an illustration as in FIG. 46, showing a two level
fusion or fixation device, percutaneously assembled in accordance
with the present invention.
FIG. 48 is a side elevational schematic view of an alternate
linkage rod in accordance with the present invention.
FIG. 49 is an enlarged exploded view as in FIG. 3A, showing the
proximal end of a bone anchor adapted for use with the linkage rod
of FIG. 48.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Although the application of the present invention will be disclosed
primarily in the context of a spinal fixation procedure, the
systems and methods disclosed herein are intended for use in a wide
variety of medical applications where the minimally invasive
implantation of an attachment, bulking, brace, support, fixation or
other prosthesis may be desirable.
One advantage of the prosthesis formation described in the various
embodiments of the present invention is the ability to access a
treatment site through minimally invasive pathways, while allowing
the formation of a relatively larger prosthesis at the treatment
site. In one embodiment, various components of a prosthesis are
inserted into a patient through minimally invasive pathways, then
joined to form a single prosthesis. This is facilitated by the
angularly adjustable connectors between the various components,
which provide leeway or angular adjustability as the components are
joined. Afterwards, the junctions between the various components
may be locked to fix or set the prosthesis in a desired
configuration.
A corollary advantage of several embodiments is the ability to
unlock and adjust one or more junctions between components of the
prosthesis, to set the prosthesis in other desirable configurations
during or even after its implantation and formation. The prosthesis
may thus be adjusted in subsequent procedures.
The systems and methods for spinal fixation according to various
embodiments of the present invention minimize procedure morbidity
by avoiding open surgical cutdowns or other invasive access
procedures. The basic percutaneous access, bone screw construction
and implantation methods, and methods and structures for
percutaneously positioning a fixation rod across bone screws, all
of which are useful in the practice of the present invention, are
disclosed in U.S. patent application Ser. No. 09/747,066, entitled
Percutaneous Vertebral Fusion System, to Teitelbaum, filed Dec. 21,
2000; U.S. patent application Ser. No. 09/943,636 to Shaolian et
al., entitled Formable Orthopedic Fixation System, filed Aug. 29,
2001; U.S. patent application Ser. No. 09/976,459 to Teitelbaum et
al., entitled Formable Orthopedic Fixation System with
Cross-Linking, filed Oct. 10, 2001; and U.S. patent application
Ser. No. 10/161,554 to Shaolian et al., entitled Formed in Place
Fixation System with Thermal Acceleration, filed May 31, 2002; the
disclosures of all of which are hereby incorporated in their
entireties by reference herein.
An overview of a system for minimally invasive posterior spinal
fixation according to one embodiment of the present invention is
provided in FIG. 1. The system includes at least two and optionally
three or four or more bone anchors 100 and a linkage rod 200. In
FIG. 1, the bone anchors are shown connected by the linkage rod
200. The system also includes a driver 150, shown engaging one of
the bone anchors 100, and an insertion tool 250, shown connected to
the linkage rod 200. Although the present invention will be
described primarily in the context of a single linkage rod
connected to two bone anchors, the normal fusion application will
involve the implantation of two linkage rods, each carried by two
or more bone anchors, bilaterally symmetrically mounted on the
spine as is well understood in the art.
FIG. 2 shows an exploded view of the bone anchor 100 and the driver
150. The bone anchor 100 is provided with threads 102 by which it
is screwed into a vertebral body. A connector 104 and a locking cap
106 are disposed within the head 108 of the bone anchor 100.
The driver 150 comprises an outer adapter 152 concentrically
arranged around an inner adapter 154. Either adapter may be freely
rotated with respect to the other. The outer adapter 152 is adapted
to engage the head 108, to screw the bone anchor 100 into a bone.
The inner adapter 154 is adapted to engage the locking cap 106, to
tighten the connector 104 within the head 108. In one embodiment,
the hexagonal proximal end 156 of the outer adapter 152 allows
torque to be applied to the outer adapter 152 by means of a wrench,
a spanner or another tool. Similarly, the hexagonal proximal end
158 of the inner adapter 154 allows torque to be applied to the
inner adapter 154.
Releasable, rotational engagement between the driver and the bone
anchor may be accomplished in any of a variety of ways. In the
illustrated embodiment, the distal end the inner adapter 154 is
provided with at least one surface for cooperating with a
complimentary surface on the proximal end of the bone anchor 100,
for transmitting torque from the inner adapter 154 to the bone
anchor 100, to enable transmission of torque from the inner adapter
154 to locking cap 106. Similarly, the distal end of the outer
adapter 152 is provided with at least one surface for cooperating
with a complimentary surface on the proximal end of the bone anchor
100, for transmitted torque from the outer adapter 152 to the bone
anchor 100 to enable credible engagement between the bone anchor
100 and the vertebral body.
In one embodiment, the bone anchor 100, its connector 104, its
locking cap 106, and the inner adapter 154 are all provided with a
central axial lumen through which a guide wire 190 may pass.
FIG. 3A is an enlarged view of the circled area in FIG. 2, showing
the proximal head 108 of the bone anchor 100 and the distal ends of
the outer adapter 152 and the inner adapter 154. The connector 104
and the locking cap 106 are disposed within the head 108. In one
embodiment, the connector 104 is spherical with an aperture 110
extending therethrough, and a gap 112 in its circumference, such
that it is approximately C-shaped when viewed along the central
axis of the aperture 110. The aperture 110 is adapted for the
insertion of a linkage rod (not shown), and has a diameter slightly
larger than that of the linkage rod. One skilled in the art will
understand that the connector 104 can be provided in a variety of
suitable shapes.
In one embodiment, the connector 104 is seated on a race or groove
114 within the head 108. The groove 114 is preferably provided with
a complementary surface to the spherical exterior surface of the
connector 104. The connector 104 may rotate on any axis within the
head 108 of the bone anchor (or bone screw) 100. A locking cap 106
may be threaded into the head 108 to lock the connector 104 against
the linkage rod 200, by compressing the groove 114, fixing the
connector 104 within the head 108. The bottom of the locking cap
106 may be provided with a concave surface (not shown) which is
complementary to the spherical exterior surface of the connector
104.
A transverse portal 116 extends through the head 108 along an axis
approximately perpendicular to the central axis of the bone anchor
100. While the aperture 110 of the connector 104 and the transverse
portal 116 of the head 108 are illustrated as circular, they may be
of different shapes in other embodiments, depending upon the cross
sectional shape of the fixation rod (e.g. oval, elliptical,
rectangular, square, etc.). The diameter of the transverse portal
116 is generally smaller than the outside diameter of the
uncompressed connector 104 but greater than the inside diameter of
the aperture 110. Before the locking cap 106 is tightened, the
connector 104 may rotate on any axis within the head 108 to
accommodate different entrance angles for the fixation rod. Thus
the central axis of the aperture 110 and the central axis of the
transverse portal 116 may be coaxial or angularly offset.
In one embodiment, the threading of the locking cap 106 into the
head 108 compresses the connector 104, decreasing the width of the
gap 112 and reducing the cross sectional area of the aperture 110.
This secures a linkage rod (not shown) extending through the
transverse portal 116 of the bone anchor 100 within the aperture
110. The tightening of the locking cap 106 into the head 108 also
fixes the rotational position of the connector 104 within the head
108.
FIG. 3B illustrates an alternate connector 104'. Similar to the
connector 104 described above, the connector 104' is provided with
an aperture 110' having a longitudinal axis and a gap 112'. The
spherical exterior surface of the connector 104' is provided with
one or two or three or more surface structures such as projections
or indentations 111. The indentations 111 receive complementary
surface structures such as projections provided within the head 108
of the bone anchor 100 to limit the degree of rotation of the
connector 104' within the head 108. For example, FIG. 3G
illustrates an exemplary embodiment wherein the complementary
surface structure comprises a pin 101 that may be laser welded or
otherwise coupled to or integrally formed with the screw head 108.
As described above, the pin 101 interacts with the indentation 111
to limit the degree of rotation of the connector 104' within the
head 108. In one specific embodiment, the connector 104' is limited
to about 30 degrees of rotation on any axis within the head 108,
from the longitudinal axis through the transverse portal 116. In
other embodiments, the connector 104' may be limited to a range of
up to about 60 degrees of rotation from the longitudinal axis. In
one embodiment, the connector 104' is limited to no more than about
5 degrees or about 10 degrees of rotation on any axis from the
longitudinal axis.
In general, the rotation of the connector 104' is limited such that
the aperture will always be exposed through transverse portal 116
to the linkage rod 200. As can be seen, for example, in FIG. 4,
below, the linkage rod 200 may be provided with a tapered distal
end 201. The tapered distal end 201 may be machined or molded
integrally with the linkage rod 200, or may be separately formed
and attached to the linkage rod 200. In one implementation, the
tapered end 201 may be a polymeric component such as nylon, HDPE,
PEBAX or other materials known in the art. The tapered tip 201
facilitates advance of the linkage rod 200 through aperture 110, by
causing the connector 104 to pivot about its center of rotation
into alignment for receiving the linkage rod 200. In this manner,
the connector 104 will self align with the linkage rod 200 to
accommodate any of a wide variety of angular relationships that may
be found in vivo.
FIG. 3C is similar to FIG. 3A above, and illustrates an inner
adapter 154' and a locking cap 106' according to another
embodiment. In one embodiment, the inner adapter 154' is provided
with a Torx distal end 158' which is adapted to engage a
complementary Torx opening 120' at the top of the locking cap 106'.
Any of a variety of complementary surface structures may be used,
as will be understood in the art in view of the disclosure
herein.
FIG. 3C illustrates a connector 104'' according to another
embodiment. Similar to the connectors 104 and 104' described above,
the connector 104'' is provided with an aperture 110'' and one or
more compressible gaps 112''. The gaps 112'' are provided with a
compressible material which compresses when the locking cap 106'
tightens the connector 104'' against the groove 114 within the head
108. Compressible material, including any of a variety of
compressible polymeric materials known in the medical device arts
can be used according to several embodiments of the present
invention. One skilled in the art will appreciate that other
suitable flexible or compressible materials may also be used. In
addition, any of a variety of metal (stainless steel, titanium,
etc.) connectors 104 may be configured such that the aperture 110
is moveable from a first, large cross-section, for receiving a
linkage rod 200 therethrough, to a second, reduced cross section
for locking the linkage rod 200 in place. This may be accomplished
by providing opposing components forming the side wall of the
connector 104 with any of a variety of interlocking structures such
as ramp and pawl ratchet structures, or sliding fit structures
which permit a reduction in the diameter in the aperture 110 under
compressive force from the locking cap 106.
In an alternate embodiment, portions or all of the connector 104
comprise a compressible media such as an open cell foam, closed
cell foam or solid compressible material. Structures comprising
polyethylene, PEEK, nylon, and other polymers known in the medical
arts may be utilized, depending upon the construction and desired
compressibility. In general, the combination of material and the
structure of the connector 104 is sufficient to allow angular
adjustment of the longitudinal axis of the aperture 110, to
accommodate various entrance angles of the linkage rod 200. After
the linkage rod 200 has been positioned within the aperture 110,
rotational and/or axial movement of a locking element such as
locking cap 106 functions to both prevent axial movement of the
linkage rod 200 within the aperture 110, as well as prevent further
angular adjustment of the longitudinal axis of the aperture 110
with respect to the longitudinal axis of the bone anchor 100.
FIGS. 3D-3F illustrate the connector 104'', the aperture 110'', the
gaps 112'', and a compressible or foldable membrane or link 115 in
greater detail. FIG. 3D is an isometric view of the connector
104''. FIG. 3E is a front plan view of the connector 104'' viewed
along the central axis of the aperture 110''. FIG. 3F is the
corresponding side plan view. In the embodiment illustrated in
FIGS. 3D-3F, the compressible link is formed by grinding, laser
etching, molding or otherwise forming a recess such as a V-shaped
channel 113 that leaves a thin link 115 which folds flat when the
connector 104'' is compressed. One of ordinary skill in the art
will understand that compressible materials and structures can be
provided in a variety of suitable shapes and forms.
In one embodiment, the apertures 110' and 110'' have a tendency to
return to their original diameters even after the connectors 104
and 104', respectively, are compressed by the locking cap 106
against the groove 114 within the head 108. This tendency results
from the resiliency of the metal, alloy or other material used to
make the connectors 104 and 104'. The use of compressible material,
such as V-shaped channels 113 in the gaps 112'' of the connector
104'', reduces or eliminates this tendency and may allow a linkage
rod (not shown) to be more firmly secured within the aperture
110''. One skilled in the art will understand that the connectors
104 and 104' can be made from lower resiliency materials which can
also reduce or eliminate the tendency of apertures 110' and 110''
to return to their original diameters.
As discussed above with reference to FIG. 2, in one embodiment, the
outer adapter 152 is adapted to engage the head 108, and the inner
adapter 154 is adapted to engage the locking cap 106. In the
illustrated embodiment, projections 156 on the distal end of the
outer adapter 152 are adapted to engage complementary projections
118 on the head 108 of the bone anchor 100. The hexagonal distal
end 158 of the inner adapter 154 is adapted to engage a
complementary hexagonal opening 120 at the top of the locking cap
106.
Although specific interlocking relationships between the driver 150
and the bone anchor 100 are illustrated herein, the present
inventors contemplate a variety of modifications. For example, the
male-female relationship between the driver and the implant may be
reversed, for either or both of the inner adaptor 154 and outer
adapter 152. In addition, each of the inner adapter 154 and outer
adapter 152 is provided with a surface structure for enabling
rotational engagement with a corresponding component on the
implant. Although this may be conveniently executed using
corresponding hexagonal male and female components, any of a
variety of alternative structures may be utilized in which a first
surface on the inner adapter 154 or outer adapter 152 cooperates
with a second, complementary surface on the corresponding aspect of
the bone anchor 100, for allowing rotational engagement, followed
by axial decoupling.
In FIG. 4, the linkage rod 200 is shown positioned within two
adjacent bone anchors 100, and released from the insertion tool
250. The insertion tool 250 is provided for the insertion of the
linkage rod 200 into the bone anchors 100. The insertion tool 250
comprises an arm 252 and a handle 254. In the illustrated
embodiment, the arm 252 is curved to facilitate insertion of the
linkage rod 200 into the bone anchors 100 within a patient along a
curved tissue tract which passes through the aperture 10 of at
least each of a first bone anchor and a second bone anchor. A
central control line 256 (shown mostly in phantom) such as a torque
transmission tube, rod or cable extends through an axial lumen of
the insertion tool 250, and terminates at a control such as a knob
258 at the proximal end of the insertion tool 250. A screw (not
shown) threaded into a tunnel 260 extending along a radius of the
knob 258 may be used to secure the control line 256 within the knob
258. The control line 256 is provided with a threaded distal tip
262. Rotating the knob 258 thus rotates the control line 256 and
its threaded distal tip 262 to engage or disengage the linkage rod
200.
In one embodiment, both the linkage rod 200 and the control line
256 are provided with a central axial lumen for the passage over a
guide wire.
FIG. 5 is an enlarged view of the circled area in FIG. 4, showing
the distal end of the outer adapter 152, the bone anchor 100, the
linkage rod 200, and the distal end of the arm 252 of the insertion
tool. The linkage rod 200 is shown fixed within the head 108 of the
bone anchor 100.
The linkage rod 200 is provided with a hexagonal proximal end 202
adapted to engage a complementary hexagonal socket (not shown) in
the distal end of the arm 252 of the insertion tool. In some
embodiments, alternative complementary surface structures may be
provided on the linkage rod 200 and the arm 252 to rotationally fix
their orientation with respect to one another. In the illustrated
embodiment, the hexagonal proximal end 202 is provided with a
dimple 204 adapted to engage a complementary nub (not shown) within
the hexagonal socket (not shown) in the distal end of the arm 252
of the insertion tool. The dimple 204 and nub (not shown) fix the
axial orientation of the linkage rod 200 with respect to the arm
252. The threaded distal tip 262 of the control line 256 may be
threaded into a complementary threaded hole 206 in the hexagonal
proximal end 202 of the linkage rod 200, enabling the linkage rod
200 to be detachably secured to the arm 252 of the insertion tool.
The threaded distal tip 262 may be threaded into the threaded hole
206 by rotating the knob (not shown) at the proximal end of the
insertion tool. Unthreading the threaded distal tip 262 from the
threaded hole 206 allows the linkage rod 200 to be released from
the insertion tool 250.
In one embodiment, the outer adapter 152 is provided with an
opening 160 extending along a diameter for fluoroscopic or other
visualization of the rotational orientation of the outer adapter
152, to align the portal 116 of the bone anchor 100 engaged by the
outer adapter 152. Towards this end, the axis of the opening 160 is
preferably arranged at a right angle to the axis of the portal 116
as shown in FIG. 5. To visualize the axial position of the outer
adapter 152 and the bone anchor 100, the inner adapter 154 may be
temporarily retracted so that it does not block the opening 160. In
another embodiment a translucent marker may be installed in opening
160 for fluoroscopic or other visualization of the outer adapter
152.
Alternatively, any of a variety of other indicium of the rotational
orientation of the bone anchor 100 may be provided. For example,
the complementary surface structures between the proximal end of
the bone anchor 100 and the distal end of the insertion tool 250
may be configured to only allow coupling between the two components
in a predetermined rotational orientation. In this construction,
visual indicia may be provided on a portion of the insertion tool
250 (e.g. "T" handle, painted or etched markings or other indicium)
which remains external to the patient, to allow direct visual
observation of the rotational orientation of the longitudinal axis
of the transverse portal 116.
FIG. 6 illustrates the described system from another angle. The
knob and its attached central cable have been removed for clarity.
The hexagonal socket 264 adapted to engage the hexagonal proximal
end 202 of the linkage rod 200, as described above, is shown. The
nub 266 adapted to engage the dimple (not shown) on the hexagonal
proximal end 202 of the linkage rod 200 is also shown.
In several embodiments, the components of the bone anchor, the
linkage rod, the driver, and the arm of the insertion tool may be
made of titanium, stainless steel or any other suitable metals,
alloys, or material. The handle of the insertion tool is preferably
made of a suitable non-slip material. The selection of these
materials for the manufacture of the components and devices
described in the above embodiments would be known by those skilled
in the art.
Methods for the minimally invasive implantation of posterior
fixation hardware according to embodiments of the present invention
are disclosed in the context of a spinal fixation procedure with
reference to FIGS. 7-45. Additional details concerning the method
are disclosed in the copending patent applications incorporated by
reference previously herein. Although the methods and instruments
of the present invention can be utilized in an open surgical
procedure, the present invention is optimized in the context of a
percutaneous or minimally invasive approach. Thus, the method steps
which follow and those disclosed in the copending patent
applications incorporated by reference herein are intended for use
in a trans tissue approach. However, to simplify the illustrations,
the soft tissue adjacent the treatment site is not illustrated in
the drawings discussed below.
In FIGS. 7 and 8, a trocar 300 is inserted through a tissue tract
and into a vertebral body 310. The trocar 300 comprises a
sharp-tipped rod (not shown) attached to a proximal or top
half-handle 302. The sharp-tipped rod is arranged concentrically
within a cannula 304, which is attached to the bottom half-handle
306 of the trocar 300. The top half-handle 302 and the bottom
half-handle 306 of the trocar 300 are screwed together for initial
use, as shown in FIGS. 7-8. The trocar 300 is inserted through the
skin, muscle and other tissues of the patient into the vertebral
body 310.
The tip 308 of the sharp-tipped rod is visible in FIG. 16.
FIG. 9 shows the bottom half-handle 306 with the attached cannula
304 embedded in the vertebral body 310. The top half-handle (not
shown) has been unscrewed and set aside from the bottom half-handle
306. In FIG. 10, a guide wire 312 is inserted into the vertebral
body 310 via the bottom half-handle 306 and the cannula 304.
In FIG. 11, the bottom half-handle 306 and the cannula 304 are
removed from the vertebral body 310. Preferably, the guide wire 312
remains in place in the vertebral body 310.
FIG. 12 shows the guide wire 312 in the vertebral body 310 after
the bottom half-handle 306 and the cannula 304 are removed.
FIGS. 13-14 show one embodiment of the invention in which an
inflatable tissue expander for enlarging the tissue tract is used.
In FIG. 13, a balloon catheter 314 carrying a balloon 316 is
advanced over the guide wire 312 towards the vertebral body 310. In
FIG. 14, the balloon 316 is inflated to dilate the tissues adjacent
the access pathway to the vertebral body 310. This provides an
enlarged path for the insertion of a sheath as described below.
In FIG. 15, a guide tube 322 is advanced over the guide wire 312
into the vertebral body 310. As shown in FIG. 16, in one
embodiment, the guide tube 322 may be approximately the same
diameter as the cannula 304 of the trocar 300, allowing the guide
tube 322 to be inserted into the opening in the vertebral body 310
created earlier by the trocar 300. The guide tube 322 acts as a
stable rail over which a tapered dilation cylinder 324 may be
advanced against the vertebral body 310.
In FIGS. 16-17, a tapered dilation cylinder 324 is advanced over
the guide tube 322 against the vertebral body 310. In one
embodiment, the tapered dilation cylinder 324 may be approximately
the same diameter as the inflated dilation balloon 316 discussed
above with reference to FIGS. 13-14. The tapered dilation cylinder
324 is used to occupy the path created by the dilation balloon, and
facilitates the insertion of a sheath. In an alternate sequence,
the dilation cylinder 324 is provided without a tapered distal end,
and is distally advanced into position directly over the inflatable
balloon.
In FIGS. 18-20, a sheath 320 is advanced over the tapered dilation
cylinder 324 against the vertebral body 310. The sheath 320
occupies the path created by the dilation balloon. Afterwards, the
guide tube 322 and the tapered dilation cylinder 324 are removed.
As shown in FIG. 20, the guide wire 312 preferably remains in the
vertebral body 310 after the placement of the sheath 320.
In FIGS. 21-23, a drill 330 having a rotatable distal tip 332 is
advanced over the guide wire 312 and through the sheath 320. The
drill 330 drills an opening (not shown) in the vertebral body 310
adapted for the insertion of a bone anchor 100. Afterwards, the
drill 330 is removed. In FIGS. 24-25, the bone anchor 100 is
advanced over the guide wire 312 and through the sheath 320 towards
the vertebral body 310.
In FIGS. 24 and 25, a bone anchor 100 is advanced over the wire 312
and through the sheath 320 into engagement with the vertebral body
310. Although the insertion tool 250 is not illustrated, the bone
anchor 100 may be coupled to the insertion tool 250 prior to the
step of advancing the bone anchor 100 into contact with the
vertebral body 310.
FIGS. 26 and 27 show the outer adapter 152 and the inner adapter
154 of the driver 150, as well as a bone anchor 100, with the
connector 104 and the locking cap 106 disposed within the head 108
of the bone anchor 100. The interrelation of these components have
been described in detail above with reference to FIGS. 2 and 3A.
The outer adapter 152 illustrated in FIGS. 26-28 additionally
comprises a pivot hole 153 which extend through a diameter of the
outer adapter 152. The pivot hole 153 is adapted for the attachment
of a guide wire insertion device 400 described in further detail
below. In FIG. 28, these components are shown arranged over a guide
wire 190.
In FIG. 28, the driver 150 (comprising the outer adapter 152 and
the inner adapter 154) is advanced over the guide wire 312 until
the driver 150 engages the bone anchor 100. In FIGS. 29 and 30,
torque is applied to the outer adapter 152 to screw the bone anchor
100 into the vertebral body 310. In FIG. 31, the driver 150 is
removed, leaving the bone anchor 100 in place, with the
longitudinal axis of the portal 116 aligned approximately parallel
with the longitudinal axis of the spine. The sheath 320, discussed
above with reference to FIGS. 18-25, while not shown in the steps
discussed with reference to FIGS. 28-31, may nonetheless be used to
shield the driver from adjacent tissue in these steps, as will be
understood by those skilled in the art.
In FIG. 32, a second bone anchor 340 has been inserted into another
vertebral body 350. While bone anchors 100 and 340 are shown
inserted into adjacent vertebral bodies 310 and 350, respectively,
the system and methods for minimally invasive spinal fixation
according to the embodiments of the present invention are also
applicable to nonadjacent vertebral bodies. For example, a first
bone anchor may be positioned in a first vertebral body as has been
described above. A second bone anchor may be positioned in a second
vertebral body, spaced apart from the first vertebral body by one
or more intervening third vertebral bodies. The first and second
bone anchors may thereafter be connected by the implantation of a
linkage rod 200. Alternatively, a third bone anchor may be
positioned in a third vertebral body, positioned in between the
first and second vertebral bodies to produce, for example, a three
level fusion system as will be discussed.
FIG. 33 shows an overview of the guide wire insertion device 400
according to one embodiment of the invention. The guide wire
insertion device comprises a handle 410 and a hollow access needle
450. The handle 410 is detachably joined to the outer adapter 152
of the driver 150. The handle 410 is forked at its proximal end
412. Each fork is provided with a pivot pin 414, which engages the
pivot hole 153 (FIG. 28) of the outer adapter 152. The forked
proximal end 412 of the handle 410 may be spread slightly to allow
the pivot pins 414 to engage the pivot hole 153. The handle 410
swings on its pivot pins 414 at the pivot hole 153 of the outer
adapter 152 of the driver 150 to insert the access needle 450
through the transverse portal 116 of the bone anchor 100.
A hollow access needle 450 is attached to the distal end 416 of the
handle 410. In one embodiment, the access needle 450 is disposed
within an opening 418 at the distal end 416 of the handle 410. A
screw (not shown) may be threaded through a screw hole 420 at the
distal end 416 of the handle 410 to tighten the access needle 450
within the opening 418. The lengthwise position of the access
needle 450 within the opening 418 is therefore adjustable to allow
the access needle 450 to be aimed through the transverse portal 116
of the bone anchor 100. In one embodiment, the access needle 450
may be aimed such that it passes through the transverse portal 116
at a point lower (towards the threads 102 in FIG. 2) than the
center of the transverse portal 116 because obstructions
encountered during the in vivo insertion of the access needle 450
may deflect the needle 450 towards the inside of its curvature and
the center of the transverse portal 116.
In several embodiments, the sharp, tapered distal end 452 of the
access needle 450 terminates at an opening 454. In one embodiment,
the access needle 450 is provided with threaded proximal end 456,
the purpose of which is described in further detail below.
FIG. 34 illustrates a flexible obturator 500 of the guide wire
insertion device 400 according to one embodiment. The obturator 500
comprises a tubing 502, a threaded cap 504 on its proximal end and
a plug 506 on its distal end. The tubing 502 is sized such that it
fits snugly within the hollow access needle 450 and occupies the
length of its lumen. The cap 504 can be made with a threaded luer
connector which may be tightened onto the threaded proximal end 456
of the access needle 450. The plug 506 may be formed from an
adhesive, for example, Loctite 3104, etc. The obturator 500
occupies the lumen of the access needle 450, and minimizes the
collection of tissue or other matter within the access needle 450
as it is advanced through the patient.
FIG. 35 shows a first guide wire insertion device 400 joined to a
first outer adapter 152 engaging a first bone anchor 100 and a
second guide wire insertion device 400' joined to the outer adapter
152' engaging a second bone anchor 340. In one embodiment, both
handles 410 and 410' are pivoted with respect to outer adapters 152
and 152' to advance access needles 450 and 450' through the
patient's tissues and towards the transverse portals 116 of bone
anchors 100 and 340, respectively. FIG. 35 also shows an obturator
500 according to one embodiment being inserted into the access
needle 450 of the guide wire insertion device 400 as described
above with reference to FIG. 34. Preferably, the obturator 500 is
inserted into the access needle 450 and threaded onto its threaded
proximal end 456 before the access needle 450 is inserted into the
patient. Likewise, another obturator 500 may be inserted into the
access needle 450'.
In one embodiment of the present invention, the guide wire
insertion device 400 additionally comprises a guide wire snare or
capture device 530, illustrated in FIG. 36. The guide wire capture
device 530 comprises an inner tubing 532 located coaxially within
an outer tubing 534. The inner tubing 532 is provided with an inner
half-cone 536 and the outer tubing 534 is provided with an outer
half cone 538. The inner half-cone 536 may be furled and retracted
within the outer tubing 534. Likewise, the outer half-cone 536 may
be furled to ease its insertion into and navigation through the
lumen of the hollow access needle 450. Inner half-cone 536 may be
rotationally oriented with respect to outer half-cone 538 to form
the conical funnel 540 of the guide wire capture device 530, as
illustrated in FIG. 37. When a guide wire contacts the conical
funnel 540 of the guide wire capture device 530, the guide wire is
directed into the lumen 542 of the inner tubing 532. The guide wire
capture device 530 also additionally comprises a handle 544 in the
illustrated embodiment.
In FIG. 38, the access needle 450 has been advanced through the
transverse portal 116 of bone anchor 100, and access needle 450'
has been advanced through the transverse portal 116 of bone anchor
340. The guide wire capture device 530 is inserted through the
lumen of the access needle 450, and its conical funnel 540 is
deployed. A guide wire 368 is inserted through the lumen of the
access needle 450' and advanced towards the conical funnel 540 of
the guide wire capture device 530. When the guide wire 368 contacts
the conical funnel 540, the guide wire 368 is directed into the
lumen 542 of the inner tubing 532 of the guide wire capture device
530.
In FIG. 39, the guide wire 368 is advanced through the lumen 542 of
the inner tubing 532 until it extends past the handle 544 of the
guide wire capture device 530 Various methods of inserting guide
wires are known in the art and the invention is not limited to the
methods disclosed herein. Instead, any method of inserting a guide
wire known to those skilled in the art may be used in accordance
with the present invention. Following placement of the guide wire
368, the first insertion device 400 and second insertion device
400' may be removed.
A flexible or curved bone drill (not shown) may be advanced along
the guide wire 368 to clear a path between the transverse portals
116 of bone anchors 100 and 340. In one embodiment, the bone drill
arm carrying the drill bit is provided with a certain degree of
flexibility to allow it to travel along the arcuate course of the
guide wire 368. In another embodiment, the curvature the bone drill
arm carrying the drill bit is matched to the curvature of the
linkage rod 200 to ensure that the path cleared between transverse
portals 116 of bone anchors 100 and 340 fits the linkage rod 200.
The bone drill is removed from the guide wire 368 after a path has
been cleared between transverse portals 116 of bone anchors 100 and
340.
In FIG. 40, a linkage rod 200 and its insertion tool 250 are shown
arranged over the guide wire 368. The linkage rod 200 and insertion
tool 250 are described above with reference to FIGS. 4-6. The
linkage rod 200 and insertion tool 250 in the embodiment
illustrated in FIG. 40 are provided with slightly different
indexing features than the linkage rod and insertion tool described
with reference to FIGS. 4-6. Referring again to FIG. 40, the
linkage rod 200 is provided with one or more bumps 220 on its
hexagonal proximal end 202. The bumps 220 are complementary with
one or more holes 280 at the distal end of the insertion tool 250.
In FIG. 40, the linkage rod 200 is detached from the insertion tool
250. The attachment of the linkage rod 200 to the insertion tool
250 is described above with reference to FIGS. 4-6.
In FIG. 41, the insertion tool 250 is used to advance the linkage
rod 200 over the guide wire 368 towards the bone anchors 100 and
340. While the linkage rod 200 is inserted from a rostral or sacral
approach (tail-to-head) in the illustrated embodiment, it may also
be inserted from a caudal approach (head-to-tail) in another
embodiment.
In FIG. 42, the linkage rod 200 is inserted through the respective
connectors 104 within bone anchors 100 and 340. The connector 104
within the bone anchor 100 is described above with reference to
FIGS. 2-3. In FIGS. 43-44, the inner adapter 154 of the driver 150
is used to tighten the locking cap 106 within the bone anchor 340,
fixing the linkage rod 200 within the bone anchor 340, as described
above with reference to FIGS. 2-3. The outer adapter 152 of the
driver 150 engages the head of bone anchor 340 to prevent it from
rotating as the locking cap is tightened. The engagement between
the bone anchor 340 and the driver 150 is described above with
reference to FIGS. 1-3 in the context of bone anchor 100.
In FIG. 44, the driver 150 (comprising the outer adapter 152 and
the inner adapter 154) is withdrawn from the bone anchor 340. The
locking cap 106 in the bone anchor 100 is similarly tightened,
fixing the linkage rod 200 within the bone anchor 100.
In FIG. 45, the insertion tool 250 is released from the linkage rod
200. The attachment and detachment of the linkage rod 200 to and
from the insertion tool 250 is discussed above with reference to
FIGS. 4-6. Afterwards, the driver 150, the sheath 320 and the guide
wire 368 are removed from the patient.
FIG. 46 illustrates the percutaneously assembled in place
prosthesis resulting from the procedure described above, comprising
the bone anchors 100, 340 and the linkage rod 200.
FIG. 47 illustrates a three level prosthesis comprising an
additional bone anchor inserted into an additional adjacent
vertebral body, to provide a three level spinal fusion.
Referring to FIGS. 48 and 49, there is illustrated an alternate
implementation of the invention. FIG. 48 illustrates a side
elevational view of a modified linkage rod 200. Linkage rod 200 in
FIG. 48 may be the same general dimensions and configuration as the
linkage rods disclosed previously herein, except as described
below. In all of the linkage rods disclosed herein, the linkage rod
200 comprises an elongate body 401 extending between a proximal end
402 and a distal end 404. The length of the body 401 in a device
intended for use in a human adult one level lumbar or lumbar-sacral
fusion, will generally be in the range from about 30 mm to about 90
mm. A linkage rod 200 intended for a two level fusion in the same
environment will generally have a length within the range of from
about 50 mm to about 110 mm.
In an embodiment of the body 401 having a circular cross sectional
configuration, the diameter of the body 401 will generally be in
the range of from about 3 mm to about 8 mm. In one embodiment, the
diameter of the body 401 in a two level fusion device is about 6.35
mm. In general, the cross sectional area of the body 401, which may
be expressed as a diameter in a circular cross sectional
implementation, may be varied depending upon the desired structural
integrity of the finished implant.
The distal end 404 of the body 401 may be provided with a distal
opening 408 to a central guidewire lumen, not illustrated. The
distal end 404 may also be provided with tapered tip 406 as has
been previously discussed. In general, the tapered tip 406 may
facilitate navigation through the tissue tract, as well as
introduction of the body 401 into the bone anchor. Tapered tip 406
may be integrally formed with the body 401, or attached thereto in
a subsequent manufacturing step.
The body 401 is generally provided with a preformed curve, such
that it forms a portion of an arc as illustrated. In certain
implementations of the invention, the arc has an approximately
constant radius of curvature along the length the body 401. The
radius of curvature of body 401 is generally in excess of about 19
cm, and, in many embodiments, within the range of from about 8 cm
to about 30 cm. In one implementation of the invention, intended
for a two level fusion, the overall length of the body 401 is about
65 mm, the diameter is about 6.35 mm, and the radius of curvature
is about 19 cm.
The radius of curvature of the body 401 may be equal or
approximately the same as the radius of curvature of the hollow
access needle 450 in the guidewire insertion device 400 discussed
previously. Thus, the radius may be approximately equal to the
distance between the access needle 450 and the pivot point 414,
which is also equal to the effective lever arm length of the handle
410. This facilitates introduction of the linkage rod 200 along the
same curved tissue tract used by or created by the access needle
450.
The linkage rod 200 illustrated in FIG. 48, unlike the embodiments
previously illustrated herein, includes a distinct distal locking
surface 410 formed by a discontinuity in the outer profile of the
body 401. In the illustrated embodiment the distal locking surface
410 is in the form of an increase in the cross sectional area of
the body 401, such as a spherical or curved enlargement of the
profile of the body 401. This distal locking surfaced 410 is
adapted to cooperate with a modified bone anchor, illustrated in
FIG. 49.
FIG. 49 is an enlarged, explored view of the proximal end of the
bone anchor and distal end of a driver tool as illustrated in FIG.
3A, except that the connector 104 has been omitted from the
embodiment illustrated in FIG. 49. Instead, the distal locking
surface 410 is adapted for insertion through the transverse portal
116 and positioning within the proximal head 108. The locking cap
106 may be threadably distally advanced into the head 108, to
compress against the distal locking surface 410 and lock the bone
anchor with respect to the linkage rod throughout any of a variety
of angular orientations, as had been discussed previously. For this
purpose, the distal wall of the chamber within the head 108 may be
provided with a complimentary curved surface for cooperating with
the distal locking surface 410. Similarly, the distal surface on
the locking cap 106 may be concave in the distal direction, to
increase the surface area of contact between the locking cap 106
and the distal locking surface 410.
A similar locking configuration may be used in connection with the
proximal bone anchor, and the proximal locking surface 412.
Proximal locking surface 412 is carried by an axially moveable
tubular collar 414. In the illustrated embodiment, the collar 414
comprises a generally tubular body axially movably carried by the
body 401 of the linkage rod 200. The proximal locking surface 412
comprises a spherical, semi-spherical, curved or other enlargement
in the cross-sectional area collar 414, to provide a locking
surface which may be useful throughout a variety of angular
orientations as has described. One or two or three or four more
axially extending slots 416 may be provided on the proximal lock,
to facilitate compression of the lock from a slideable orientation
to a locked orientation in which it is compressed against the body
401. In the illustrated embodiment, two or more axially extending
slots extend in a proximal direction from the distal end of the
lock.
In use, the linkage rod 200 is advanced distally along a guidewire,
through a tube, or otherwise through the first and second bone
anchors. With the distal locking surface 410 positioned within the
proximal head 108 of the distal bone anchor, the locking cap 106 of
the distal bone anchor is tightened to lock the linkage rod 200
with respect the distal bone anchor. The proximal lock is
thereafter axially distally advanced along the insertion tool
and/or linkage rod 200, until the proximal locking surface 412 is
positioned within the head 108 of the proximal bone anchor. The
locking cap 106 of the proximal bone anchor is tightened, to lock
the proximal locking surface 412 against the body 401.
The proximal lock may be distally advanced along the insertion tool
and/or linkage rod 200 in any of a variety of manners, such as by
distally advancing a pusher sleeve which is axially movably carried
on the insertion tool.
In one embodiment, the transverse portal 116 of the proximal bone
anchor is provided with a proximal opening having a first diameter
and distal opening having a second, smaller diameter. The outside
diameter of proximal locking surface 412 is dimensioned relative to
the portal 116 such that it can pass through the proximal opening
on the transverse portal 116 but cannot pass distally through the
distal opening of the transverse portal 116. In this manner, the
clinician can perceive tactile feedback once the proximal lock has
been distally advanced into position within the head 108. This same
construction can be utilized on the distal bone anchor as well,
such that distal advancement of the distal locking surface 410 may
be accomplished until the positive stop is felt by the clinician as
the distal locking surface 410 is seated within the head 108. The
driver tool can be provided with indicium of the rotational
position of the bone anchor.
In all of the foregoing embodiments, the insertion tool may be
provided with a curved distal region, having a radius of curvature
which approximates the radius of curvature of the linkage rod,
described above. Thus, in one embodiment both the linkage rod 200
and the distal portion of the insertion tool are provided with a
curve having a radius of approximately 12 cm. This further
facilitates introduction of the linkage rod and insertion tool
along a curved tissue tract, while minimizing trauma to surrounding
tissue, as the linkage rod 200 is navigated through the first and
second bone anchors.
The foregoing construction also allows the percutaneous access site
for the introduction of the linkage rod 200 to be predetermined
distance from the longitudinal axis of the driver 150. For example,
in one implementation of the guidance system, the radius of
curvature of the curved needle 450 is approximately 9 cm. This
enables the percutaneous access site to be approximately 8
centimeters from the percutaneous entry site for the driver 150.
The transdermal access site for the linkage rod is preferably no
more than about one radius away from the driver 150. This allows
minimization of the length of the tissue tract, and thus minimizes
the access induced trauma to surrounding tissue.
Not all of the steps described above are critical to the minimally
invasive implantation of posterior fixation hardware. Accordingly,
some of the described steps may be omitted or performed in an order
different from that disclosed. Further, additional steps may be
contemplated by those skilled in the art in view of the disclosure
herein, without departing from the scope of the present
invention.
The present inventors contemplate the interchangeability of and
recombination of various structural and method elements in the
foregoing description. For example, the guidewire may be positioned
through portals of adjacent bone anchors utilizing either the
procedures disclosed in the copending patent applications
previously incorporated by reference herein. Alternatively, the
guidewire may be positioned utilizing the pivotable guidance system
disclosed herein. As a further alternative, a tubular sleeve may be
advanced over the guidewire and through the portals on bone anchors
100, with the guidewire thereafter removed. The linkage rod 200 may
thereafter be advanced through the tubular sleeve.
The linkage rod 200 may be advanced utilizing the manual insertion
tool 250, as disclosed herein. Alternatively, the linkage rod 200
may be releasably connected to the distal end of a curved pivotable
arm 450, using releasable connection structures disclosed elsewhere
herein. In this manner, the pivotable insertion system such as that
illustrated in FIG. 33 can be utilized to insert the linkage rod
200 through one or more apertures 116 in one or more bone anchors
100.
The various materials, methods and techniques described above
provide a number of ways to carry out the invention. Of course, it
is to be understood that not necessarily all objectives or
advantages described may be achieved in accordance with any
particular embodiment described herein. Thus, for example, those
skilled in the art will recognize that the components of the system
may be made and the methods may be performed in a manner that
achieves or optimizes one advantage or group of advantages as
taught herein without necessarily achieving other objectives or
advantages as may be taught or suggested herein.
Although the present invention has been described in terms of
certain preferred embodiments, other embodiments of the invention
including variations in dimensions, configuration and materials
will be apparent to those of skill in the art in view of the
disclosure herein. In addition, all features discussed in
connection with any one embodiment herein can be readily adapted
for use in other embodiments herein. The use of different terms or
reference numerals for similar features in different embodiments
does not imply differences other than those which may be expressly
set forth. Accordingly, the present invention is intended to be
described solely by reference to the appended claims, and not
limited to the preferred embodiments disclosed herein.
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